| 摘要 |
PURPOSE:To perform an accurate load control by inputting a voltage corresponding to the power source voltage existing between high/low potentials and driving a sensor with the current or voltage according to a variation of the power source voltage. CONSTITUTION:When a voltage on the voltage dividing point made by resistors R1, R2 in a constant current circuit 2 is expressed as Vin, a negative feed back is effected by an operational amplifier 9 so that the voltage Vin is appeared on a connected point for a resistor R3 and a semiconductor pressure sensor 3. So, when a DC source voltage is constant, the voltage Vin is made to be constant and the voltage appeared on the connected point for the resistor R3 and the sensor 3 is also made to be constant. Then, the sensor 3 is driven by a constant driving current I=Vin/R3. When the DC source voltage is varied, the voltage Vin is also varied at the same rate as the variation rate of the DC source voltage. Consequently, a sensor output varied at the same rate as the variation rate of the DC source voltage is obtained from the sensor 3. Therefore, the sensor output and a digital amount converted by an A/D converter 6 making the DC source voltage as a reference voltage are accurately corresponded, thereby the accurate information of sensor output is transmitted to a microcomputer 5. |
